Conventionally, a photographic development method and a screen printing method have been used for forming an etching resist, a solder resist, and marking for a printed wiring board.
In the photographic development method, patterning is performed by applying a photosensitive resin material and a photomask on a substrate, exposing the photosensitive resin to light to photo-cure only in parts without being covered with the photomask, and dissolving an uncured photosensitive resin material in a developer. A solder resist and marking materials are further cured by heating or the like. As to an etching resist, a copper foil in a region not covered with the etching resist is removed by etching, for obtaining wiring pattern. On the other hand, in the screen printing method, pattern formation is performed by using a stencil to allow an ink to be transferred by a squeegee, wherein it is difficult to obtain a highly fine pattern.
In order to simplify wiring patterning, an inkjet method has been used in recent years (Patent Literatures 1 to 4). This method is a method including drawing a conductor circuit pattern on a metal foil provided on a plastic substrate by using an inkjet printer. By the method, an etching resist is prepared, with which an etching treatment is carried out. In the inkjet method, CAD data can be sent to the printer in advance. Therefore, accurate printing can be performed with respect to the metal foil, and also positioning is easily made. In addition, when the inkjet method is used, a wiring pattern can be directly drawn on the metal foil. Accordingly, it is possible to significantly reduce labor and time required for a step of manufacturing a printed wiring board, compared with those for the photographic development method and the screen printing method, and consumables such as a developer, a resist ink, and a cleaning solvent can be reduced, as advantages of inkjet printing.
Furthermore, it is proposed to use an inkjet printer for printing a solder resist, which is for protecting a conductor circuit formed on a printed wiring board (Patent Literatures 5 and 6). The formation/printing method is the same as the wiring patterning except that a subject to be printed is the printed wiring board on which the conductor circuit has already been formed. The solder resist is printed on a portion of the printed wiring board, where soldering for mounting parts is not performed. Also in this case, the use of inkjet printer helps to use the number of treatment steps, time, and consumables to be used, compared with the use of photographic development method or the screen printing method.
In addition to the above, proposals are made to use a system in which a plurality of steps are performed by a single ink jet printer provided with ink tanks, separately for an etching resist ink, a solder resist ink, a marking ink, and corresponding curing agents for these (Patent Literature 7).